Chonkified Cat Scratcher Cardboard Cutter

Changes

1. It's markedly longer
   • + Helps the guide establish a firmer footing
   • + Helps so your hand is less likely to catch on the cardboard; cardboard cuts are no fun
2. It's also taller (more space between the cardboard guide and the grip top)
   • That way, if the edge of your hand does hang off the edge of it, you have more leeway before the cardboard fights back
   • Allows you to wrap a fingertip around the end of it, if you need to pull harder on some troublesome cardboard
   • Your hand doesn't feel so scrunched if you're gripping this thing for a while
3. Other ergonomic tweaks
   1. Added somewhat finger-shaped grooves.  They ended up being way bigger than my fingers, but they still give you more non-parallel surfaces to brace against
   2. Chunkier form to fill your grip more, as your fingers wrap around
   3. Slight bend near palm-side top of grip, so there's not a fully square edge
4. I modified the screw hole so that an M5 will slide through.  I secure it on the other side with a nut.
5. (3mf file, PrusaSlicer) I modified a few sections to use fuzzy skin.  Looks great, improves grip.
6. I oriented mine standing up.  I think most slicers can handle the overhang angle these days.

Update 2025-02-11 ("V9")

1. Widened the blade-installation chute in the beginning.
2. Narrowed the bolt hole just a smidge, so the M5 should cut its own threads, rather than need a nut.
3. Projected a small (0.25mm) outline groove of the internal blade path, both to aid in finagling it in and out of there, and to make it more instantly obvious where the blade is inside if you get turned around.
4. To test my changes, I derived a chopped down sample chunk of the model, keeping mostly only the blade path and screw hole, to test tolerances.  This is the file “test shark”, because I think it ended up looking kind of like a cartoon shark.  I thought it might be helpful to those who want to check the tolerances/clearances themselves before printing the whole thing.

Remix It

I imported the original model's STL, referenced the basic rough dimensions of it, and went from there.

You can find it in OnShape: https://cad.onshape.com/documents/4ad323462260062bfe9022d7/w/e1e699151ec44c1c117070d0/e/44952f1699fc4e24270da344?renderMode=0&uiState=679afd237fe6bf510ab5dd1b